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[Xen-devel] [PATCH net-next v3 1/9] xen-netback: Introduce TX grant map definitions



This patch contains the new definitions necessary for grant mapping.

v2:
- move unmapping to separate thread. The NAPI instance has to be scheduled
  even from thread context, which can cause huge delays
- that causes unfortunately bigger struct xenvif
- store grant handle after checking validity

v3:
- fix comment in xenvif_tx_dealloc_action()
- call unmap hypercall directly instead of gnttab_unmap_refs(), which does
  unnecessary m2p_override. Also remove pages_to_[un]map members
- BUG() if grant_tx_handle corrupted

Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>

---
 drivers/net/xen-netback/common.h    |   25 ++++++
 drivers/net/xen-netback/interface.c |    1 +
 drivers/net/xen-netback/netback.c   |  163 +++++++++++++++++++++++++++++++++++
 3 files changed, 189 insertions(+)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index d218ccd..f1071e3 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -79,6 +79,11 @@ struct pending_tx_info {
                                  * if it is head of one or more tx
                                  * reqs
                                  */
+       /* callback data for released SKBs. The callback is always
+        * xenvif_zerocopy_callback, ctx points to the next fragment, desc
+        * contains the pending_idx
+        */
+       struct ubuf_info callback_struct;
 };
 
 #define XEN_NETIF_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
@@ -108,6 +113,8 @@ struct xenvif_rx_meta {
  */
 #define MAX_GRANT_COPY_OPS (MAX_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE)
 
+#define NETBACK_INVALID_HANDLE -1
+
 struct xenvif {
        /* Unique identifier for this interface. */
        domid_t          domid;
@@ -126,13 +133,23 @@ struct xenvif {
        pending_ring_idx_t pending_cons;
        u16 pending_ring[MAX_PENDING_REQS];
        struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
+       grant_handle_t grant_tx_handle[MAX_PENDING_REQS];
 
        /* Coalescing tx requests before copying makes number of grant
         * copy ops greater or equal to number of slots required. In
         * worst case a tx request consumes 2 gnttab_copy.
         */
        struct gnttab_copy tx_copy_ops[2*MAX_PENDING_REQS];
+       struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
+       struct gnttab_unmap_grant_ref tx_unmap_ops[MAX_PENDING_REQS];
 
+       spinlock_t dealloc_lock;
+       spinlock_t response_lock;
+       pending_ring_idx_t dealloc_prod;
+       pending_ring_idx_t dealloc_cons;
+       u16 dealloc_ring[MAX_PENDING_REQS];
+       struct task_struct *dealloc_task;
+       wait_queue_head_t dealloc_wq;
 
        /* Use kthread for guest RX */
        struct task_struct *task;
@@ -221,6 +238,8 @@ int xenvif_tx_action(struct xenvif *vif, int budget);
 int xenvif_kthread(void *data);
 void xenvif_kick_thread(struct xenvif *vif);
 
+int xenvif_dealloc_kthread(void *data);
+
 /* Determine whether the needed number of slots (req) are available,
  * and set req_event if not.
  */
@@ -228,6 +247,12 @@ bool xenvif_rx_ring_slots_available(struct xenvif *vif, 
int needed);
 
 void xenvif_stop_queue(struct xenvif *vif);
 
+/* Callback from stack when TX packet can be released */
+void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success);
+
+/* Unmap a pending page, usually has to be called before xenvif_idx_release */
+void xenvif_idx_unmap(struct xenvif *vif, u16 pending_idx);
+
 extern bool separate_tx_rx_irq;
 
 #endif /* __XEN_NETBACK__COMMON_H__ */
diff --git a/drivers/net/xen-netback/interface.c 
b/drivers/net/xen-netback/interface.c
index 8d6def2..7170f97 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -37,6 +37,7 @@
 
 #include <xen/events.h>
 #include <asm/xen/hypercall.h>
+#include <xen/balloon.h>
 
 #define XENVIF_QUEUE_LENGTH 32
 #define XENVIF_NAPI_WEIGHT  64
diff --git a/drivers/net/xen-netback/netback.c 
b/drivers/net/xen-netback/netback.c
index addfe1d1..7c241f9 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -771,6 +771,19 @@ static struct page *xenvif_alloc_page(struct xenvif *vif,
        return page;
 }
 
+static inline void xenvif_tx_create_gop(struct xenvif *vif, u16 pending_idx,
+              struct xen_netif_tx_request *txp,
+              struct gnttab_map_grant_ref *gop)
+{
+       gnttab_set_map_op(gop, idx_to_kaddr(vif, pending_idx),
+                         GNTMAP_host_map | GNTMAP_readonly,
+                         txp->gref, vif->domid);
+
+       memcpy(&vif->pending_tx_info[pending_idx].req, txp,
+              sizeof(*txp));
+
+}
+
 static struct gnttab_copy *xenvif_get_requests(struct xenvif *vif,
                                               struct sk_buff *skb,
                                               struct xen_netif_tx_request *txp,
@@ -1599,6 +1612,105 @@ static int xenvif_tx_submit(struct xenvif *vif)
        return work_done;
 }
 
+void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success)
+{
+       unsigned long flags;
+       pending_ring_idx_t index;
+       u16 pending_idx = ubuf->desc;
+       struct pending_tx_info *temp =
+               container_of(ubuf, struct pending_tx_info, callback_struct);
+       struct xenvif *vif =
+               container_of(temp - pending_idx, struct xenvif,
+                       pending_tx_info[0]);
+
+       spin_lock_irqsave(&vif->dealloc_lock, flags);
+       do {
+               pending_idx = ubuf->desc;
+               ubuf = (struct ubuf_info *) ubuf->ctx;
+               index = pending_index(vif->dealloc_prod);
+               vif->dealloc_ring[index] = pending_idx;
+               /* Sync with xenvif_tx_action_dealloc:
+                * insert idx then incr producer.
+                */
+               smp_wmb();
+               vif->dealloc_prod++;
+       } while (ubuf);
+       wake_up(&vif->dealloc_wq);
+       spin_unlock_irqrestore(&vif->dealloc_lock, flags);
+}
+
+static inline void xenvif_tx_dealloc_action(struct xenvif *vif)
+{
+       struct gnttab_unmap_grant_ref *gop;
+       pending_ring_idx_t dc, dp;
+       u16 pending_idx, pending_idx_release[MAX_PENDING_REQS];
+       unsigned int i = 0;
+
+       dc = vif->dealloc_cons;
+       gop = vif->tx_unmap_ops;
+
+       /* Free up any grants we have finished using */
+       do {
+               dp = vif->dealloc_prod;
+
+               /* Ensure we see all indices enqueued by all
+                * xenvif_zerocopy_callback().
+                */
+               smp_rmb();
+
+               while (dc != dp) {
+                       pending_idx =
+                               vif->dealloc_ring[pending_index(dc++)];
+
+                       /* Already unmapped? */
+                       if (vif->grant_tx_handle[pending_idx] ==
+                               NETBACK_INVALID_HANDLE) {
+                               netdev_err(vif->dev,
+                                       "Trying to unmap invalid handle! "
+                                       "pending_idx: %x\n", pending_idx);
+                               continue;
+                       }
+
+                       pending_idx_release[gop-vif->tx_unmap_ops] =
+                               pending_idx;
+                       gnttab_set_unmap_op(gop,
+                                       idx_to_kaddr(vif, pending_idx),
+                                       GNTMAP_host_map,
+                                       vif->grant_tx_handle[pending_idx]);
+                       vif->grant_tx_handle[pending_idx] =
+                               NETBACK_INVALID_HANDLE;
+                       ++gop;
+               }
+
+       } while (dp != vif->dealloc_prod);
+
+       vif->dealloc_cons = dc;
+
+       if (gop - vif->tx_unmap_ops > 0) {
+               int ret;
+               ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
+                               vif->tx_unmap_ops,
+                               gop - vif->tx_unmap_ops);
+               if (ret) {
+                       netdev_err(vif->dev, "Unmap fail: nr_ops %x ret %d\n",
+                               gop - vif->tx_unmap_ops, ret);
+                       for (i = 0; i < gop - vif->tx_unmap_ops; ++i) {
+                               netdev_err(vif->dev,
+                                       " host_addr: %llx handle: %x status: 
%d\n",
+                                       gop[i].host_addr,
+                                       gop[i].handle,
+                                       gop[i].status);
+                       }
+                       BUG();
+               }
+       }
+
+       for (i = 0; i < gop - vif->tx_unmap_ops; ++i)
+               xenvif_idx_release(vif, pending_idx_release[i],
+                               XEN_NETIF_RSP_OKAY);
+}
+
+
 /* Called after netfront has transmitted */
 int xenvif_tx_action(struct xenvif *vif, int budget)
 {
@@ -1665,6 +1777,27 @@ static void xenvif_idx_release(struct xenvif *vif, u16 
pending_idx,
        vif->mmap_pages[pending_idx] = NULL;
 }
 
+void xenvif_idx_unmap(struct xenvif *vif, u16 pending_idx)
+{
+       int ret;
+       struct gnttab_unmap_grant_ref tx_unmap_op;
+
+       if (vif->grant_tx_handle[pending_idx] == NETBACK_INVALID_HANDLE) {
+               netdev_err(vif->dev,
+                               "Trying to unmap invalid handle! pending_idx: 
%x\n",
+                               pending_idx);
+               return;
+       }
+       gnttab_set_unmap_op(&tx_unmap_op,
+                       idx_to_kaddr(vif, pending_idx),
+                       GNTMAP_host_map,
+                       vif->grant_tx_handle[pending_idx]);
+       ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
+                       &tx_unmap_op,
+                       1);
+       BUG_ON(ret);
+       vif->grant_tx_handle[pending_idx] = NETBACK_INVALID_HANDLE;
+}
 
 static void make_tx_response(struct xenvif *vif,
                             struct xen_netif_tx_request *txp,
@@ -1726,6 +1859,14 @@ static inline int tx_work_todo(struct xenvif *vif)
        return 0;
 }
 
+static inline int tx_dealloc_work_todo(struct xenvif *vif)
+{
+       if (vif->dealloc_cons != vif->dealloc_prod)
+               return 1;
+
+       return 0;
+}
+
 void xenvif_unmap_frontend_rings(struct xenvif *vif)
 {
        if (vif->tx.sring)
@@ -1814,6 +1955,28 @@ int xenvif_kthread(void *data)
        return 0;
 }
 
+int xenvif_dealloc_kthread(void *data)
+{
+       struct xenvif *vif = data;
+
+       while (!kthread_should_stop()) {
+               wait_event_interruptible(vif->dealloc_wq,
+                                       tx_dealloc_work_todo(vif) ||
+                                        kthread_should_stop());
+               if (kthread_should_stop())
+                       break;
+
+               xenvif_tx_dealloc_action(vif);
+               cond_resched();
+       }
+
+       /* Unmap anything remaining*/
+       if (tx_dealloc_work_todo(vif))
+               xenvif_tx_dealloc_action(vif);
+
+       return 0;
+}
+
 static int __init netback_init(void)
 {
        int rc = 0;

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